$ F = \left[\begin{array}{rrr}2 & 0 & 0 \\ 0 & 0 & 2 \\ 1 & 1 & 2\end{array}\right]$ What is $ F^{-1}$ ?
Solution: $ = \left[\begin{array}{rrr}\frac{1}{2} & 0 & 0 \\ -\frac{1}{2} & -1 & 1 \\ 0 & \frac{1}{2} & 0\end{array}\right]$